It has become common in electronic devices having a display screen such as mobile communication terminals (cellular phones) that the display unit be configured with a touch panel and the user touches the screen for input. The touch panel allows for a more intuitive input operation and provides a useful input method particularly to mobile communication terminals having smaller keys.
Mobile communication terminals have become multifunctional and carry multiple types of radio devices. More specifically, they generally carry not only radio devices for voice telephone calls and data communication, which are the main functions of mobile communication devices, but also multiple radio devices for reception of one segment broadcast and radio communication with Bluetooth (registered trademark) and wireless LAN.
These radio devices are used by switching the reception or communication frequency. The operation frequency varies depending on the frequency used and may interfere with the touch panel drive frequency. In such a case, the detection of touch to the touch panel is influenced and the touching may not be detected properly, forcing the user to retry.
Touch panel detection errors occur often due to the influence of the above external factors. Techniques for reducing detection errors, for example, by taking into account environmental change such as temperature change (for example, Patent Literature 1) or by changing detection conditions depending on whether the back light is ON or OFF (for example, Patent Literature 2) have been proposed.